1. Field of the Invention
The present invention relates to methods and apparatuses for dispensing powdered material. More particularly, the invention relates to methods and apparatuses for dispensing of powdered material in a time-efficient, precise manner.
2. Description of Related Art
Numerous industries, including, among others, pharmaceutical and medical industries, frequently deal with minute quantities of powdered material. Accordingly, efficiency and accuracy of dispensing apparatus has become particularly important. However, the majority of the known powder dispensers fall short of satisfying the needs of the market.
The main criterion defining the accurate dispensing of powdered material is the uniform weight of multiple dosages of the powdered material. The weight of the dispensed powdered material is directly proportional to its dispensed volume and density. Typically, a volume of powdered material is presumed to have its known true density, which is thus often viewed as a constant during dispensing of multiple dosages of the powdered material. Based on this premise, many of the known apparatuses rely on controlling the flow of powdered material to attain the uniform weight of multiple dispensed dosages. For many types of powdered material, however, even distribution of particles in a given volume and therefore the density of particles in this volume are far from being uniform. As a consequence, quite often the weight of individual dosages of powdered material may vary from dosage to dosage. Needless to say, even miniscule deviations of the weight of the dispensed dosage of powdered material, used, for example, for drug preparation, from the target weight may result in serious negative effects.
Due to the complex nature of powdered materials, it is difficult to ascertain the flow properties of a given powdered material which causes processing difficulties. Apparently identical powdered materials may vary from batch to batch or supplier to supplier. Transportation conditions can dramatically alter the packing condition from a highly aerated state at one extreme to a hard-consolidated condition at the other. Free-flowing powders may be prone to segregation, attrition and electro-static charge. Attrition for example can change particle shape, remove surface coatings, produce fines and result in bulk density changes.
Powders may be unintentionally changed during storage, handling and processing. In storage, for example, powders may consolidate under their own weight; during transportation, vibration can produce a similar or even worse level of solidification; and during processing, while powdered material flows from a powder-containing vial through a material processing mechanism into a material-receiving vial, particles may either adhere to guiding surfaces or agglomerate around the adhered particles, gradually reducing and eventually affecting the flow uniformity. Furthermore, some types of powdered material can be compacted under their own weight thereby affecting density along the column of the stored powdered material with relatively low density at the top of the column and relatively high density at the bottom thereof.
Thus, efficient processing of powdered materials depends upon flow rates, levels of compaction, vibration levels, the head of material in a hopper type of conveying surface and environmental conditions. All these factors are important in determining the consistency and efficiency of processing. Attaining the uniform density of powdered material to be dispensed in multiple dosages may drastically affect the importance of these difficult to control factors. While numerous attempts have been directed to controlling, for example, flow rates, density control has been largely ignored. As a result, accurate and rapid dispensing of powdered materials remains problematic, particularly in industries dealing with minute amounts of powdered material.